Thanks for your time and feedback mate!
I'd heard horror stories about over-scoping in game jams, so I purposefully kept it as minimal and bare-bones as possible for this one!
If I had more time, the next iterations would fall into two camps:
Polish and presentation: Sprite sheets for more characterful animations, a fleshed out dock scene, more immersive sound design.
Core Gameplay loop: Add more upgrades/side-grades, different oceans with higher-tier loot but with equipment requirements, random events like storms, sharks, seasickness which require some kind of player skill-check to overcome, and can offer some kind of reward.
Other: Give the character some more context, probably through their interaction with the world. Perhaps some NPCs so we can see how the other inhabitants of the world see the character. This is definitely out of scope for a jam though!